I saw your response to the topic of grinding and sanding stainless without warping. I have a few questions about this topic. To give you a little background in what I know and have done; I am a welder who doesn't usually do much sheet metal. I find it very frustrating due to how it warps so easily. I have tried 5 different butt welds on some tables/counter tops in commercial kitchens and a 2 dishwashers troughs in SS work station tables.

I have issues with warping when welding and grinding.

-I am using a Miller Dynasty 300 DX with scratch start (not my equipment and I hate TIG welding without a foot pedal). In the past I have used vise grips with 1/4 long aluminum channel on each side of the seam.

-I tack the seam with no gaps and making sure the two surfaces are even.

-I then slowly weld it every inch or so and have to cool it down with water from the back side in order to pull it opposite of the welded side.

-After it is welded then I get to the part I absolutely dread is grinding and polishing it. I can do fine except the occasional underfilled spots or where it buckled and I have to take a center punch and hammer backed up with a flat piece of steel a hundred times.

-I am using a large 9 inch grinder with some various grit flexable disks to get it flush. Then I go over it with one of those multiple layered sanding wheels to get the grain. It does a decent job, which is exceptable by the guy who hires me to do the work.

-As I grind I have to make a couple of passes and then start cooling it down with water on the opposite side to get the bubble out.

My question is by reading this what can I do more to prevent warping.

-Do I need different tools
Such as hammers and dollies
-Do I need to put a bar on the back of the weld
-Do I need to clamp it down better
-Do I need better grinding equipment
-Are there better ways to remove the weld without grinding
-Do I need to change my welding amps, I have tryed any where from 35-50 amps with 1/16 309L filler.

I know that you said to put a 1/4 gap at the end of the weld, but that seems like a huge gap, unless it shrinks that much as you weld it.

If you can give me any suggestions I would be greatly appreciative because I have a few jobs coming up really soon.

ehy..
i think we spoke on the phone..
i have found a wonderful tool for getting into the hard to reach corners of the bottom of sinks..
a dnafile with a 1/8" scotch blendex belt wow works great..
any more questions you need feel free to let me know,,,
opening my own stainless shop in the spring..(2009)
its beeen quite some time since i was on here..
sorry Bud..i try to be more regular!

back up the bottome of the weld with some 1/2" alum flatbar(clamped)
keep the but weld gapped at the far end..it will close as you tack it across .this is tricky as it will start to close the gap as your tacks are cooling you want to time it so when you get to the far end it just closes..this keep the weld from buckling before you even get it welded..
never cool with water ..unless it to late and you are trying to shrink it..water cools way to fast..use your chiller bars (1/2" alum flat bar and 2X2 by 1/4 alum angle )..you can even put them in the cooler(kitchens have the walk-ins)
only add filler rod if you need it..i use .03. filler rod and weld about 45 amps (scratch) i wait for the but weld material to almost fail to bead then i add..rarey do i have to do this more than once across a weld..But i understand with both sides of the butt weld being cut with a grinder it could be tough..try to use a sanding disc to get them even straighter..this can be very important..
also..your grinder is too big..a 4.5" grinder is good..if you can get a 4.5 inch grinder that is variable like the bosch or metabo i have used they are great..you can slow the grinder right down and add way less heat to the material..less heat equals less warping..
when you grind..graining or smoothing or the initial grind..do not hover over a spot..like painting(spray) always moving the grinder over the material never slowing or stopping..
if you have to hit a spot a little more start from one end and move across just adding more pressure in that spot..
if you cant run your hand on the material after you just ground it. you have gotten it to hot,,
let it cool a bit between passes of move a little faster to avoid putting to much heat into it..
just finished a sink and counter top unit today..
free staning with 24" X 18" sink 12" deep
four legs 4.5" back splash and 2 " counter front return..
the customer was so happy they went and got me a bottle of wine and a six pack of beer,,
i cant remember the last time i saw some customers so excited and pleased..
sorry no pics..
bye for now ..
sorry bout the hijack!